Reclamation of molded sand

ABSTRACT

Lumpy molded sand from a shake-out operation is fed onto the upper section of an endless conveyor which moves the material through a stream of projected abrasive particles thereby granulating the lumps. The granulated sand and abrasive particles are conveyed to a separator which removes the grains of sand from the abrasive particles.

te States Patent 1 Carmen Get. 30, 1973 RECLAMATION 0F MOLDED SAND [76]Inventor: James H. Carpenter, 212 Pangborn B1vd., Hagerstown, Md. 21740[22] Filed: Jan. 3, 1972 [21] Appl. No.2 214,700

[52] US. Cl. 241/68, 241/301, 241/DlG. 1O [51] int. Cl. B02c 19/00 [58]Field 01 Search 241/5, 22, 68, 69,

241/77, 263, 265, 273.1, 274, DIG. 10, 301;

[56] References Cited UNITED STATES PATENTS 894,272 7/1908 Jorn, Jr51/14 1,907,198 5/1933 Hull 5l/14 2,261,947 11/1941 Bamebl et al.241/DlG. 10 2,924,912 2/1960 Schulte 51/14 Primary Examiner-Granville Y.Custer, Jr. Attorney-David E. Dougherty et al.

[ 5 7 ABSTRACT Lumpy molded sand from a shake-out operation is fed ontothe upper section of an endless conveyor which moves the materialthrough a stream of projected abrasive particles thereby granulating thelumps. The granulated sand and abrasive particles are conveyed to aseparator which removes the grains of sand from the abrasive particles.

10 Claims, 4 Drawing Figures 3.768.740 sum 2 n? 5 PATENTED U61 3 0 I975PATENTEU BB! 3 0 I915 SHEET 30F 3 ll H H RECLAMATION OF MOLDED SANDBACKGROUND OF THE INVENTION The present invention relates to apparatusfor the reclamation of sand used to produce molds for foundry castings.

Reconditioning of used sand involves reducing used core elements andmolded sand lumps to grains. It is necessary to remove metallicparticles, sintered clusters of sand grains, excess fines and trampmaterial from the sand prior to reuse. The quality of reclaimed sandmust be comparable to that of new sand so that it may be satisfactorilysubstituted for new sand in core and molding sand mixtures withoutappreciable change in sand practice. Thus, it is usually necessary toremove accumulated coatings from around individual sand grains.

Recently, foundries are converting to a practice which utilizes qualitysand. In this practice a chemical binder and a catalyst are mixedtogether and hardened into a solid cake at ambient temperatures to forma chemically bonded mold. Since baking is not required, this process isknown in the art as no-bake molding. The no-bake molding process hasdistinct advantages such as ease of making a mold, a cleanerenvironment, ease of handling a completed mold, and improved castingfinishes and casting tolerances.

Despite the numerous advantages, there are a number of disadvantagessuch as the increased cost for 'quality grade sand. Efficient andeffective reclamation of the used sand is necessary to make the no-bakeprocess economically attractive. Reclamation systems of the prior artsuch as hammer mills, ring crushers, jaw or roll crushers generallysubject moving parts to excessive wear and large stresses, therebydecreasing machine life and increasing machine breakdowns. The largequantity of dust created by prior apparatus is not only an undesirablepollutant but is evidence that the lumps are crushed to such an extentthat a good yield of granulated sand is sacrificed. Heretofore,apparatus of the prior art has not effectively and efficiently reclaimedsand from lumps.

SUMMARY OF THE INVENTION A feed mixture of lumps of molded sand togetherwith contaminants such as spent abrasive, rods, and fines from ashake-out operation is fed onto the upper section of an endless conveyorwhich provides for a positive drive of the feed material through astream of projected abrasive particles. The endless conveyor is of thetype having a plurality of perforated slats held between a pair oflaterally aligned endless chains. The abrasive particles and sand passthrough the perforations in the slats and are conveyed to a separator inwhich the granulated sand is removed for further processing orrecycling. Trash, core rods, and feed material of a larger size than theperforations in the slats are discharged by the conveyor.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view showingone embodiment of the present invention;

FIG. 2 is an end elevational view of the embodiment shown in FIG. 1;

FIG. 3 is a cross-sectional view along the line 3-3 of FIG. 1; and

FIG. 4 is a cross-sectional view along the lines 44 which are shown inFIG. 3.

DETAILED DESCRIPTION A feed mixture from a shake-out operation whichincludes lumps of molded sand and may include core rods, hangers, trampiron of various sizes, sweepings and spillage is fed into a hopper 11positioned above the conveyor I3.

One method of forming the feed mixture comprises projecting abrasiveparticles against a mold with the casting therein to remove the sand androds from the casting and clean the exposed casting in one operation.This is accomplished in a blast chamber with the sand, rods, spentabrasive, fines and other contaminants falling through the bottom of thechamber from where it is conveyed onto the conveyor 13.

In general, the feed mixture from the hopper 11 drops onto slats 15which form the upper, running surface of the conveyor 13. The slats 15are held between a pair of spaced parallel chains 17. The upper surfaceof the conveyor l3 passes through a trough 19 which includes the inletsection communicating with the hopper 11 and an enclosed blastingchamber 2!. On either side of the blasting chamber 21, the trough 19includes a plurality of rubber curtains 23 which hang from the top ofthe trough 19 to prevent the escape of projected abrasive particles.

A stream of abrasive particles is projected in a path toward the upperor running surface of the conveyor 13 within the blasting chamber 21.The blasting path extends along the length of the trough 19 and theupper surface of the conveyor 113. A centrifugal blasting wheel 25 whichis mounted on the shaft of a motor 27 has a shot path disposedlengthwise with respect to the flow of lumps. In this case, the hottestarea of the blast stream is aimed downwardly toward the trough 19. Topermit an increased width of the conveyor 13 and an increased flow offeed material through the path of projected abrasive particles, it ispreferable to have centrifugal blasting wheels 25 mounted side by side.The lumps of molded sand are granulated in the blasting chamber 21.

The granulated sand and abrasive particles pass through the perforations29 in the floor 31 of respective slats 15 and are pushed along thebottom of the trough 19. The granulated sand and abrasive particles aredischarged through an opening into a hopper 33. Trash, core rods, andmaterial larger than the perforations 29 in the slats 15 are dischargedfrom the upper surface of the conveyor 13 onto the floor as the slats l5begin their return run. This material can be removed by suitable meanssuch as another conveyor or stored in a receptacle.

The sand and shot mixture which passes into the hopper 33 flows througha conduit 37 to a conditioner 39 which subjects the mixture containingsand to a scouring treatment thereby removing accumulated coatings onthe sand grains. The conditioner 39 includes a centrifugal throwingwheel which projects the sand and shot against an impact plate. Afterscouring the sand is conveyed via elevator 41 into an air wash separator43 which separates the sand from the shot. Although FIGS. 1 and 2illustrate an embodiment wherein the mixture including sand and shot ispassed through a conditioner 39 prior to separation, it is contemplatedthat the mixture including sand and shot can be conveyed directly to theair wash separator 41 without passing through a conditioner 39. Thislatter arrangement is preferable when it is desirable to separate thesand from the shot prior to conditioning the sand.

Advantageously, at least a pair of separators 413 of the air wash typesuch as described and illustrated in U.S. Pat. No. 3,368,677 areutilized. In general, the air wash separator 43 subjects the fallingmixture to a cross current of air. A number of skimmer plates areprovided in a separating chamber to facilitate a separation of themixture into individual streams in accordance with their weight. in thisrespect the abrasive particles are heavier than the sand which in turnis heavier than the tines. Thus, the abrasive particles fall generallydirectly downwardly into a discharge conduit 45 while the tine grainsand is slightly diverted and received in other discharge conduits 47.Other discharge conduits 48 are conveniently provided for fines andother contaminants.

The substantially pure abrasive particles are received in conduit orhopper 45 for reuse by centrifugal blasting wheels 25. The granulatedreclaimed sand passes through conduit 47 to a magnetic drum separator 49to remove the small quantity of metal abrasive that may be mixed withthe otherwise substantially pure sand. From the magnetic separator 49the pure sand flows through outlet 51 to a bin 53 for storage ordirectly to a sand molding area for reuse.

in some cases, especially with green foundry sand, it is desirable torecycle the pure sand from the outlet several times through aconditioner 39 to obtain the desired organic level or clay content. Toachieve this end, the sand from the outlet can be recycled into theelevator 41. However, in many cases, the rate of sand flow will notallow this extra load on the conditioner 39 and separators 43. ifconsiderable recycling is required, the sand may be fed into anauxiliary conditioning system including a plurality of conditionersarranged in series.

According to the principles of the present invention, the upper orconveying surface comprises a plurality of perforated slats extendingbetween laterally aligned endless chains 17 which are trained about aplurality of sprockets 55. The sprockets 55 are rotatably mounted on aframe 57. A suitable drive means such as an electric motor 59 is indriving engagement with a pair of the sprockets 55 which serve as drivesprockets while the remaining sprockets 55 are idler sprockets. Theupper section of the conveyor moves through the trough 19 so as to movelumps of molded sand through the blasting station 21. At least some ofthe slats 15 include an upper rib 63 which extends upwardly across theslat 15. The upper rib 63 functions to hold the lumps against the forceof the blast stream so as to drive the lumps through the blast stream.The perforations 29 in the floor 31 of each of the slats 15 are ofsufficient size to permit the passage of granulated sand and abrasiveparticles. The floor 31 is spaced from the bottom of the trough 19 sothat granulated sand and shot drop to the bottom of trough 19. At leastsome of the slats 15 include a lower rib 61 extending downwardly acrossthe floor 31. The bottom edge of the lower rib 61 is spaced just abovethe bottom end of the trough 19 and conforms therewith so as to push orscrape granulated sand and spent abrasive particles along the bottom ofthe trough 19.

Each slat 15 includes a pair of side walls 65 which contain projectedand ricocheting abrasive particles.

The lower portion of each of the side walls 65 overlap the respectivesides 67 of the trough 19 so as to contain abrasive particles and sandwithin the trough 19. The upper portion of each of the side walls 65 issecured to a slat support member as by suitable means such as bolts. Theslat support member 69 includes a vertically extending plate portion 73which extends above the side walls 65.

The trough 19 includes a channel 75 exterior and on either side ofrespective sides 67 for housing respective chains 17. The support member69 includes a lower portion having a pair of depending members 77 witheach of the members 77 disposed on a respective side of the chain E7.The bottom of depending member 77 forms a support on which brackets 79are mounted. The brackets 79 are mouned to every other link of the chain17 by a pin 83. Each of the brackets 79 on a respective side of thechain 117 is secured to the support member 69 by bolts 85. Each of thechains 17 rides on a track 81 secured to the bottom of the channel 75.

A scrapper member 87 in the form of a plate is mounted on either side ofthe track 81 to respective depending members 77 of the support member69. The bolt 85 holds respective scrapper members 87 in place. Thescrapper members 87 are provided for cleaning the channel 75 of anyabrasive or sand which might become deposited therein.

The outer wall 89 of the channel 75 extends exterior to the supportmember 69 so as to enclose the support member 69 and associated parts.The upper end of the outer wall 89 of the channel '75 is provided withan overlapping member 73 so as to contain abrasive within the trough 19.

In operation, the feed material is conveyed along the upper surface ofthe conveyor 13 through the blast chamber 21. The granulated sand andabrasive particles which pass through the perforations 29 in the slats15 are pushed along the bottom of the trough 19 by the lower ribs 61. Inthe interest of efficiently minimizing the wear throughout the system,it is preferable to maintain a steady flow of feed material at a maximumcapacity. in this case, the abrasive particles are projected against thematerial held within the slats 15 rather than the slats l5 themselves.Therefore, the wear on the slats 15 will be minimized. To achieve thisend, it is preferable to use a hopper 1 l at the entrance of theconveyor for providing a reservoir of lumps to insure a steady influx offeed material.

Preferred embodiments of the present invention having been describedherein, it is to be recognized that modifications, variations andchanges therein will be apparent to one of ordinary skill in the art. itis contemplated that the claims appended herewith will cover suchmodifications, variations and changes that are within the broad spiritand scope of the present invention.

What is claimed is:

1. Apparatus for granulating lumps of molded sand comprising: (a) atrough; (b) an endless conveyor having a running surface passing throughsaid trough and spaced from the bottom thereof; (0) means for projecting abrasive particles in a path toward said running surface forgranulating lumps of molded sand thereon,-said running surface beingperforated to permit granulated sand and abrasive particles to passtherethrough to the bottom of said trough; and ((1) means for removingsaid granulated sand and abrasive particles from the bottom of saidtrough.

2. Apparatus according to claim 1 wherein said endless conveyor includesa plurality of ribs extending upwardly from said running surface forholding lumps of 5 molded sand against the force of projected abrasiveparticles.

3. Apparatus according to claim 1 wherein said removing means comprisesa plurality of ribs extending downwardly from said running surface topush sand and abrasive particles along the bottom of said trough.

4. Apparatus according to claim 1 wherein said projecting meanscomprises a centrifugal throwing wheel.

5. Apparatus according to claim 1 wherein said endless conveyorcomprises a plurality of slats forming the running surface, each slatbeing perforated.

6. Apparatus according to claim 5 wherein at least some of said slatsinclude an upper rib for holding the lumps of molded sand against theforce of projected abrasive particles.

7. Apparatus according to claim 5 wherein at least some of said slatsinclude a lower rib for pushing sand and abrasive particles along thebottom of said trough.

8. Apparatus according to claim 5 wherein said trough includes anenclosed blasting chamber housing said projecting means, an inlet forlumps of molded sand, and an opening in the bottom of the trough fordischarging sand and abrasive particles.

9. Apparatus according to claim 5 wherein said endless conveyorcomprises a plurality of slats forming the running surface and a pair ofspaced parallel chains for holding said slats therebetween, said troughincluding a channel along each side thereof for housing a respectivechain.

10. Apparatus for reclaiming sand from a feed mixture including lumps ofmolded sand comprising: (a) a trough; (b) an endless conveyor having arunning surface passing through said trough and spaced from the bottomthereof; (c) means for projecting abrasive particles in a path towardsaid running surface for granulating lumps of molded sand thereon, saidrunning surface being perforated to permit granulated sand and abrasiveparticles to pass therethrough to the bottom of said trough; (d) meansfor removing said granulated sand and abrasive particles from the bottomof said trough; and (e) a separator for removing the granulated sandfrom the mixture of granulated sand and abrasive particles.

1. Apparatus for granulating lumps of molded sand comprising: (a) atrough; (b) an endless conveyor having a running surface passing throughsaid trough and spaced from the bottom thereof; (c) means for projectingabrasive particles in a path toward said running surface for granulatinglumps of molded sand thereon, said running surface being perforated topermit granulated sand and abrasive particles to pass therethrough tothe bottom of said trough; and (d) means for removing said granulatedsand and abrasive particles from the bottom of said trough.
 2. Apparatusaccording to claim 1 wherein said endless conveyor includes a pluralityof ribs extending upwardly from said running surface for holding lumpsof molded sand against the force of projected abrasive particles. 3.Apparatus according to claim 1 wherein said removing means comprises aplurality of ribs extending downwardly from said running surface to pushsand and abrasive particles along the bottom of said trough. 4.Apparatus according to claim 1 wherein said projecting means comprises acentrifugal throwing wheel.
 5. Apparatus according to claim 1 whereinsaid endless conveyor comprises a plurality of slats forming the runningsurface, each slat being perforated.
 6. Apparatus according to claim 5wherein at least some of said slats include an upper rib for holding thelumps of molded sand against the force of projected abrasive particles.7. Apparatus according to claim 5 wherein at least some of said slatsinclude a lower rib for pushing sand and abrasive particles along thebottom of said trough.
 8. Apparatus according to claim 5 wherein saidtrough includes an enclosed blasting chamber housing said projectingmeans, an inlet for lumps of molded sand, and an opening in the bottomof the trough for discharging sand and abrasive particles.
 9. Apparatusaccording to claim 5 wherein said endless conveyor comprises a pluralityof slats forming the running surface and a pair of spaced parallelchains for holding said slats therebetween, said trough including achannel along each side thereof for housing a respective chain. 10.Apparatus for reclaiming sand from a feed mixture including lumps ofmolded sand comprising: (a) a trough; (b) an endless conveyor having arunning surface passing thrOugh said trough and spaced from the bottomthereof; (c) means for projecting abrasive particles in a path towardsaid running surface for granulating lumps of molded sand thereon, saidrunning surface being perforated to permit granulated sand and abrasiveparticles to pass therethrough to the bottom of said trough; (d) meansfor removing said granulated sand and abrasive particles from the bottomof said trough; and (e) a separator for removing the granulated sandfrom the mixture of granulated sand and abrasive particles.